The purpose of this lesson is to introduce students to the idea of chemical reactions. This lesson focuses on evidence of chemical reactions and how to identify if a reaction has occurred. As the first lesson in this unit on chemical reactions, the primary goal is to engage students and get them excited about exploring how chemical reactions are involved in every aspect of life. Students will have many opportunities to learn in this lesson, including identifying chemical reactions they have encountered in their daily life, exploring the process of food rotting, and seeing chemical reactions take place through a lab activity. Students will also learn how to describe the reactions they see using chemical equations. Students will be assessed formatively in this lesson, through class discussion, monitoring student progress, and students' analysis of the laboratory activity.
Objectives
Students will be able to:
Describe physical and chemical changes that they see
Recognize evidence of chemical changes by describing the changes that occur.
Identify observable signs that a chemical reaction has occurred
Determine whether or not a reaction has occurred based on their observations
Distinguish between reactants and products in a chemical equation
Explain what happens in a chemical reaction using the properties of the reactants and products as evidence
Where's the Evidence? Lab Materials (for each lab bench):
4 100 mL beakers
candle
Spatula
sugar
Tongs
Matches
sodium carbonate (powdered solid)
Graduated cylinder, 10ml
Test tubes (2)
Aluminum foil, about 10-cm square
Test tube rack
1 M hydrochloric acid (HCl) in a dropper bottle
0.1 M Copper Sulfate (CuSO4) solution
0.1 M Sodium Carbonate (Na2CO3) solution
Instruction
Opening (20 minutes)
When students walk into the classroom, two things will be written on the board: the Chemistry Checkpoint question and the objectives for the days lesson.
Chemistry Checkpoint: List and describe two chemical reactions you experience in your daily life.
Each class begins with a Chemistry Checkpoint Question to work on for the first five minutes of class. This particular Chemistry Checkpoint activates prior knowledge and asks students to relate their life to the new topic we are about to study. I will call on a few students to share what they wrote. Some students will have more background knowledge than others on chemical reactions. This will serve as a formative assessment because I will be able to see what students already know, what I need to cover more clearly, and I will be able to track their progress throughout the unit. This will lead into the introduction of the lesson.
First I will take out a ripe tomato, cut in half. In an interactive discussion, I will ask the class to name some of the properties of the ripe tomato. Next I will ask them to predict what happens when the tomato rots. Does it look different? Does it feel different? What happens inside the tomato to make it rot? After listening to a few answers, I will explain that tomatoes rot due to a chemical reaction involving micro-organisms that feed of the compounds in the tomato to create new compounds.
I will take out another tomato that is cut in half, this time the tomato will be rotten. I will ask students to describe what they see. Can a rotten tomato be transformed into a ripe tomato? Students will say no, and I will explain that this is because many chemical reactions cannot be reversed. Looking at this rotten tomato, how can we tell that a chemical reaction has occurred? Many reactions provide evidence that they have occurred, just like this tomato's color changed and mold formed on the surface of the tomato.
Very nice opening. Why not let the students know at this point about the day's topic and their objectives for the day? .
Middle (60 minutes)
Activity 1:
Our class discussion about tomatoes and how chemical reactions can be observed will lead into a PowerPoint that describes evidence of chemical changes and the basic form in which chemical reactions are represented.
As I present notes in the form of a PowerPoint Presentation, I will keep students engaged by asking them questions, as opposed to just flipping from slide to slide. Some examples of questions I may ask include:
From or experience with the rotting tomato and any other experiences you have had, what do you think are some indications that a chemical reaction has occurred?
Do phase changes show signs of a chemical reaction? Why or why not? What is the difference between a physical change and a chemical change? Have you defined these terms?
Let's think about the word reactants. What do you think of when you hear that word? What whaabout products? I will guide them to come up with the fact that reactants react to form something new, called a product
What do you think students will have difficulty with in this opening discussion? Do you think they will actually understand the idea that products are "new substances?" What questions will you use to assess their understandings?
Activity 2:
I will pass out Where's the Evidence? Lab assignment to each student. I will go over the safety precautions and give instructions for the experiment. I will briefly go through what students are expected to do and demonstrate how to handle the hydrochloric acid, as it can be dangerous to work with. Before letting the students get to work, I will make sure they understand what they are required to do and how they are expected to handle the chemicals.
What specifically will you demonstrate?
Students will break up into their designated partners and begin the experiment. How will you group the students? If you are going to assign partners, you should include this assignment list in your "materials needed" list.
When students get to their lab benches, they will be set up with all the materials they will need. As students begin their experiment, I will walk around the classroom and observe each group. I will be available to help students who have questions, but my primary purpose will be to ask students probing questions that will make them think about each step of the experiment. I will make sure students make a prediction about what they think will happen when they carry out each reaction before they actually mix the reactants. This will help students make sense of what they are doing and why it is important. Good
As I am walking around asking questions and making clarifications, I will be monitoring student progress as formative assessment. I will also be paying close attention to students to make sure they are being safe and responsible with the lab materials, especially the chemicals, as they can be dangerous if they are not used appropriately.
Once students complete their lab activity, they will clean up their lab benches and go back to their seats. I will instruct the students who have finished to work quietly at their seats on the analysis and conclusion of their experiment while we wait for the entire class to finish. Are you satisfied that the instructions on your lab sheet will lead to a product you are happy with? If not, how might you make your expectations more clear?
I will supervise the proper disposal of all materials and make sure students clean up safely. Why not cover this before the lab so that students know what they are supposed to do and how?
Closing (10 minutes)
Once everyone is cleaned up and back in their seats, I will wrap up the lesson by asking students to share their observations. I will ask them if they expected all the outcomes or if they were surprised by any of the reactions. Students will share their experiences with the class. As a class, I will try to address a few of the analysis questions to make sure students came out of the experiment with the correct experiences.
Let's take a closer look at the second reaction we did: sugar + heat. What did you predict would happen when we put the sugar over the flame? Is that what happened? (I predict that students will think the sugar will melt, and that they will believe that it did melt. If this is the case, I will continue with the following questions). Is melting a chemical or a physical change? If the sugar melted, then it is a change of state. What do we know about changes of state? Chemical or physical change? Students will answer that it is a physical change. If it's a physical change, then did a reaction really occur? No. What if I asked you if the sugar really melted? Could anything else have happened to the sugar? Instead of saying the sugar melted, someone describe to me what you SAW when the sugar was placed over the flame? What did it look like? Water. Could the sugar have turned into water? The answer is yes. In this case, the sugar reacted with heat and oxygen in the air to create water. Does anyone know the other product of this reaction? (Some students may know, I assume that most will not). I will tell them that a gas was also released in this reaction but it is colorless and odorless, so we can not detect it using the tools we had. I will write the chemical equation of the combustion of sugar on the board (C12H22O11 + 12 O2 ---------> 12 CO2 + 11 H2O) and tell students that we will be learning more about the different types of chemical reactions in the following lessons.
I will sum up the lesson by revisiting the day's objectives and summarizing what we learned about the evidence of chemical reactions and how we can represent chemical reactions using chemical equations.
The closing of each class will be the same every time. In order to reflect on the class and determine the main point, as a class we will come up with a one-two sentence summary of the class. I will ask the students to write this down each day in order to use it in future classes, as well as to use as a study guide for the unit test.
"If you had to summarize the main idea of today's lesson, what would you say? As a class let's come up with a few sentences to summarize what we learned today and why it is important."
In the last two minutes of class I will tell the students that their homework is to finish their Where's the Evidence? Lab analysis and conclusion questions and to read section 10.1 of their textbook and take notes. I will tell them that next class we will be taking a deeper look into chemical equations and we will learn about how to write balanced chemical equations. When are they going to turn in their lab work?
Nice lesson, Shara. You should note what you think the main points of the lesson are, and then focus your closing questions to assess where students are . Can they distinguish between chemical and physical changes? Can they name examples of each? Are physical/chemical process always straight forward or common sense? What comprises evidence that a chemical reaction has occurred? What are the key differences between reactants and products? etc.
Title: Introduction to Chemical Reactions
Summary
The purpose of this lesson is to introduce students to the idea of chemical reactions. This lesson focuses on evidence of chemical reactions and how to identify if a reaction has occurred. As the first lesson in this unit on chemical reactions, the primary goal is to engage students and get them excited about exploring how chemical reactions are involved in every aspect of life. Students will have many opportunities to learn in this lesson, including identifying chemical reactions they have encountered in their daily life, exploring the process of food rotting, and seeing chemical reactions take place through a lab activity. Students will also learn how to describe the reactions they see using chemical equations. Students will be assessed formatively in this lesson, through class discussion, monitoring student progress, and students' analysis of the laboratory activity.Objectives
Students will be able to:Materials
Instruction
Opening (20 minutes)
Very nice opening. Why not let the students know at this point about the day's topic and their objectives for the day? .
Middle (60 minutes)
Activity 1:What do you think students will have difficulty with in this opening discussion? Do you think they will actually understand the idea that products are "new substances?" What questions will you use to assess their understandings?
Activity 2:
- I will pass out Where's the Evidence? Lab assignment to each student. I will go over the safety precautions and give instructions for the experiment. I will briefly go through what students are expected to do and demonstrate how to handle the hydrochloric acid, as it can be dangerous to work with. Before letting the students get to work, I will make sure they understand what they are required to do and how they are expected to handle the chemicals.
What specifically will you demonstrate?Closing (10 minutes)
Nice lesson, Shara. You should note what you think the main points of the lesson are, and then focus your closing questions to assess where students are . Can they distinguish between chemical and physical changes? Can they name examples of each? Are physical/chemical process always straight forward or common sense? What comprises evidence that a chemical reaction has occurred? What are the key differences between reactants and products? etc.
Notes